Your best bet is to upgrade to the latest version if you can.
I have the same issue so I created a script to run as a nightly job to delete this file. The script is:
net stop semsrv
net stop SQLANYs_sem5
attrib -r "C:\Program Files (x86)\Symantec\Symantec Endpoint Protection Manager\db\sem5.log"
del "C:\Program Files (x86)\Symantec\Symantec Endpoint Protection Manager\db\sem5.log"
net start SQLANYs_sem5
net start semsrv
But like I said, best course of action is to upgrade to latest version